From the Guidelines
Cyclobenzaprine (Flexeril) is the least sedating effective muscle relaxer, typically prescribed at 5-10 mg doses taken up to three times daily as needed for acute muscle spasms. This recommendation is based on the evidence from a higher-quality Cochrane review that found skeletal muscle relaxants, including cyclobenzaprine, to be moderately superior to placebo for short-term pain relief 1. While all muscle relaxers can cause some degree of drowsiness, cyclobenzaprine at lower doses (5 mg) tends to produce less sedation than alternatives like carisoprodol (Soma) or methocarbamol (Robaxin).
Some key points to consider when prescribing cyclobenzaprine include:
- Starting with the lowest effective dose to minimize sedation
- Taking the medication 1-2 hours before bedtime to reduce daytime sedation
- Avoiding alcohol and other central nervous system depressants to prevent increased sedation
- Monitoring for adverse events, as skeletal muscle relaxants are associated with a higher total number of adverse events and central nervous system adverse events compared with placebo 1
Tizanidine (Zanaflex) is another option with potentially less sedation when used at lower doses (2-4 mg), but the evidence for its efficacy in acute low back pain is based on 8 trials, and its sedation profile may vary depending on the individual patient 1. Overall, cyclobenzaprine is a reasonable choice for patients who require a muscle relaxer with minimal sedation, due to its relatively selective action on central nervous system pathways that control muscle tone.
From the FDA Drug Label
Cyclobenzaprine reduced or abolished skeletal muscle hyperactivity in several animal models Analysis of the data from controlled studies shows that cyclobenzaprine produces clinical improvement whether or not sedation occurs. The incidence of drowsiness, the most frequent adverse reaction, was similar with both drugs.
The least sedating best muscle relaxer is not explicitly stated in the provided drug labels. However, cyclobenzaprine is shown to produce clinical improvement whether or not sedation occurs, suggesting it may be a viable option for muscle relaxation with potentially less sedation compared to other drugs like diazepam.
- Key points:
From the Research
Least Sedating Muscle Relaxers
- Methocarbamol and metaxalone are considered to be less sedating compared to other muscle relaxants, although evidence of their effectiveness is limited 3
- Cyclobenzaprine is a commonly used muscle relaxant, but it can cause sedative effects in some patients, with over 30% of patients experiencing drowsiness 4
- Tizanidine is also known to have sedative properties, which may be beneficial for patients with insomnia caused by severe muscle spasms, but it can cause dry mouth and other adverse effects 5, 3
Comparison of Muscle Relaxants
- There is no clear evidence that one muscle relaxant is superior to another in terms of efficacy, and the choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions 5, 3
- Cyclobenzaprine has been evaluated in the most clinical trials and has consistently been found to be effective for various musculoskeletal conditions, but it can cause dizziness and drowsiness 5, 6
- Baclofen, tizanidine, and dantrolene are effective for treating spasticity, but they can cause adverse effects such as weakness, dry mouth, and hepatotoxicity 5
Mechanism of Action
- Cyclobenzaprine's mechanism of action is not fully understood, but it is thought to mediate its effects centrally via inhibition of tonic somatic motor function, likely through modulation of noradrenergic and serotonergic systems 4
- Cyclobenzaprine has also been found to exhibit high-affinity noncompetitive antagonism at the histamine H1 receptor, which may contribute to its sedative effects 4